beta-Lipotropin is a 90-amino acid polypeptide that is the carboxy-terminal fragment of POMC. It stimulates melanocytes to produce melanin, and can also be cleaved into smaller peptides including opioid peptides: gamma-lipotropin, alpha-MSH, beta-MSH, gamma-MSH, alpha-endorphin, beta-endorphin, gamma-endorphin and met-enkephalin.